Abstract The Archean atmosphere is thought to have been devoid of oxygen but, instead, containing high concentrations of greenhouse gases, such as CO2 and possibly CH4, that were required to keep the Earth surface environments warm enough for maintenance of liquid water under faint-young-Sun conditions. Earlier studies have suggested that the CO2 concentrations must have been as high as over 1000 times present atmospheric levels (PAL) to overcome the effects of weaker solar luminosity. However, more recent studies of Precambrian paleosols imply existence of at least tenfold-lower, but still high pCO2 levels. The appearance of minute amounts of atmospheric O2 at the transition of Archean and Proterozoic is well documented, however, the bulk composition of the atmosphere and its dynamics at this crucial time is still widely debated. Different paleoclimate proxies of the ~2.45 Ga Kuksha paleoweathering crust suggest its formation in a cool, temperate climate. Paleoatmospheric pCO2 estimates by geochemical and isotopic mass-balance models suggest remarkably low paleoatmospheric CO2 levels, with the best guess estimates of atmospheric CO2 between 1 and 10 PAL. We speculate that the Kuksha paleoweathering crust either predates, or partly overlaps with, the onset of Huronian glaciation and corresponds to a time interval of low CO2 level during the first recorded large glaciation in Earth history.

中文翻译：

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在 2.45 Ga 古风化壳中记录的大氧化事件开始时的 CO2 下降和冷却

摘要 太古代大气被认为缺乏氧气，但含有高浓度的温室气体，如 CO2 和可能的 CH4，这些气体是保持地球表面环境足够温暖以在微弱的年轻状态下维持液态水所必需的。 - 阳光条件。早期的研究表明，二氧化碳浓度必须高达当前大气水平 (PAL) 的 1000 多倍，才能克服较弱的太阳光度的影响。然而，最近对前寒武纪古土壤的研究表明存在至少低 10 倍但仍然很高的 pCO2 水平。在太古宙和元古代过渡期间出现的微量大气 O2 有据可查，但是，在这个关键时刻大气的整体成分及其动力学仍然存在广泛争议。~2.45 Ga Kuksha 古风化地壳的不同古气候代表表明它是在凉爽的温带气候中形成的。通过地球化学和同位素质量平衡模型估算的古大气 pCO2 表明古大气 CO2 水平非常低，对大气 CO2 的最佳估计估计值在 1 到 10 PAL 之间。我们推测 Kuksha 古风化地壳早于或部分重叠于休伦期冰期的开始，并且对应于地球历史上第一次记录的大冰期期间低 CO2 水平的时间间隔。对 1 到 10 PAL 之间的大气 CO2 的最佳猜测估计。我们推测 Kuksha 古风化地壳早于或部分重叠于休伦期冰期的开始，并且对应于地球历史上第一次记录的大冰期期间低 CO2 水平的时间间隔。对 1 到 10 PAL 之间的大气 CO2 的最佳猜测估计。我们推测 Kuksha 古风化地壳早于或部分重叠于休伦期冰期的开始，并且对应于地球历史上第一次记录的大冰期期间低 CO2 水平的时间间隔。